This invention is directed to avionic systems and, more particularly, to the avionic systems that are used to guide aircraft, in particular jet aircraft.
In the past, because avionic systems have not had the ability to continuously determine the correct speed necessary to obtain the most economical operation during a flight, simplified speed schedules, which approximate maximum economy under average conditions, have been developed. During climb, a constant Mach/airspeed approximation tending to minimize climb time for heavier takeoff weights has usually been adopted. During cruise, most airlines select a constant Mach number giving a reasonable balance between fuel and flight time related costs for the major routes flown by the airlines. During descent, constant Mach/airspeed schedules are used, and the pilot's judgment is relied upon to minimize descent undershoot or overshoot.
As fuel prices have risen, the constant speed approximations discussed in the preceding paragraph have lost validity because economical speeds now vary more with gross weight (and burnoff) than they previously did. The fuel penalty of off-optimum operation, which can occur by following constant speed approximations, has become severe enough to create a desire for a means of providing better information for use by either a pilot or an autopilot so that the most economical flight profile can be followed during the climb, cruise and descent phases of a flight.
While various attempts have been made to provide economy aircraft guidance information in pilot or autopilot usable form, these attempts have had a number of disadvantages. In many of the suggested pilot systems, the produced information has not been given to pilots in an easily usable form, requiring minimum effort on the pilot's part. Further, many of these systems, regardless of whether adapted for use by pilots or autopilots, have not been able to accommodate differing fuel prices, time costs and schedule constraints that vary from airline to airline and route to route. Moreover, in general, these systems have not dealt effectively with variations between individual aircraft in the areas of thrust, drag, lift, instrumentation, etc.
Therefore, it is an object of this invention to provide a new and improved avionic system that is useful in guiding an aircraft so that a predetermined flight profile is readily followed.
It is another object of this invention to provide a new and improved avionic system adapted to guide an aircraft along the most economical flight profile between a departure airport and a destination airport.
It is another object of this invention to provide a new and improved avionic system adapted to guide an aircraft along the most economical flight profile that takes into consideration factors such as fuel price, time costs, variations between individual aircraft in thrust, drag, instrumentation, etc.
It is yet another object of this invention to provide an avionic system suitable for use in an aircraft to provide information in readily usable pilot form that allows a pilot to fly the most economical flight profile between takeoff and landing, with minimal effort.